1. Field of the Invention
The present invention relates to display apparatus and display method for performing displaying of an image using picture elements or xe2x80x9cpixelsxe2x80x9d as disposed in a matrix fashion. In particular, the invention relates to a liquid crystal display device and EL display device of the active matrix type.
2. Description of the Related Art
Recently, the technology has been rapidly developed for fabrication of semiconductor devices with a semiconductor thin film being formed on a glass substrate of low cost, such as for example thin-film transistors (TFTs). The reason for this is that the needs for liquid crystal display devices of the active matrix type are increasing more and more.
The active-matrix type liquid crystal display device is such that TFTs are disposed respectively in several tens or several millions of pixel regions that are disposed in a matrix manner, which TFTs have their switching functions to control electrical charge carriers exiting from or entering to a respective one of pixel electrodes.
FIG. 1 shows a configuration of a liquid crystal display device of the active matrix type in the prior art. A shift register and buffer circuitry are typically called the xe2x80x9cperipheral driver circuitxe2x80x9d in general; in the recent years, this is integrally formed on the same substrate together with an active matrix circuit.
Disposed in the active matrix circuit are thin-film transistors which utilize amorphous silicon as formed on a glass substrate used.
A configuration has also been known wherein quartz is utilized as the substrate while employing a polycrystalline silicon film for fabrication of such thin-film transistors. In this case both the peripheral driver circuit and active matrix circuit will be constituted from those thin-film transistors formed on the quartz substrate.
In addition, a thin-film transistor fabrication technology is also known which makes use of a crystalline silicon film on a glass substrate by utilizing laser anneal techniques or the like. Use of this technology may enable integration of the active matrix circuit and its associated peripheral driver circuit on the glass substrate.
In the configuration shown in FIG. 1A, an image signal being supplied to an image signal line is selected at a timing as indicated by FIG. 1B in response to a signal from a shift register circuit (horizontal scanning shift register) of a source line side driver circuit. And, certain image signal will be supplied to a corresponding source signal line.
The image signal which was supplied to the source signal line is then selected by the thin-film transistor of a pixel to be written into a specified pixel electrode.
The pixel thin-film transistor is operable in response to a selection signal that is supplied via a gate signal line from a shift register (vertical scanning shift register) of a gate line side driver circuit not shown herein.
The above operation will be recurrently carried out with the setting of appropriate timings determinable depending on a signal from the shift register of the source line side driver circuit and a signal from the shift register of the gate line side driver circuit to thereby sequentially write information into respective pixels of the matrix shape.
After completion of writing of image information corresponding to a single screen, image information is then written for the next screen. In this way, displaying of images will be performed in a sequential order. Generally, such writing of this one-screen information is repeated for thirty times or alternatively sixty times per second.
In recent years, as the information amount increases rapidly, an attempt has been made to attain an increase in display capacity as well as an increase in precision of display image resolution. Here, some major examples of the display resolution standards as generally employable in computers will be indicated along with pixel numbers and standard titles.
Today, even in the field of personal computers, software program packages have become widely available which perform a plurality of display operations different in nature from one another on the display screen; accordingly, a shift has been made to those display devices which are higher in display resolution than VGA and SVGA standards to accommodate the XGA and SXGA standards.
Furthermore, the prescribed liquid crystal display devices of high display resolution have also been employed for use in displaying television broadcast signals other than displaying of data signals in such personal computers.
As is well known, the currently available television signals may generally be classified into several groups which are based on the NTSC scheme, PAL scheme, and SECAM scheme. The NTSC television scheme has the degree of image resolution which is 525 in scanning-line number (effective scan line number is approximately 480). The PAL and SECAM schemes are 625 in scan line number (effective scan line number is 576).
In cases where an image based on television signals of the NTSC scheme or PAL scheme or alternatively SECAM scheme is to be visually indicated on a liquid crystal display device that accommodates the SVGA or XGA or SXGA standard stated supra, it will be required that an image non-display section (image-absent area on the screen) be provided due to a difference in resolution among them.
Now refer to FIGS. 2A and 2B. FIGS. 2A and 2B are schematical diagrams of liquid crystal display devices of the peripheral driver circuit integration type that are designed to accommodate the XGA standard. In FIG. 2A, reference numeral 201 is a source side driver circuit. 202 is a gate line side driver circuit. 203 is a TFT active matrix circuit section. In FIG. 2B numeral 207 is a sourceside driver circuit. 208 is a gate line side driver circuit. 209 is a TFT active matrix circuit section.
In the case of displaying an image based on a television signal of the PAL scheme on the liquid crystal display device accommodating the XGA standard, an image display section 204 and image non-display sections 205 and 206 are required as shown in FIG. 2A.
Alternatively, in the case of displaying an image based on a television signal of the NTSC system on the liquid crystal display device accommodating the XGA standard, a display section 210 and its surrounding image non-display section 211 are required as shown in FIG. 2B.
It will be desirable that the image non-display sections 205, 206 and 211 be designed to display the complete black color in order to maximally enhance a visual difference from the image display sections 204 and 210.
In the related art an attempt has been made to let the image non-display sections be colored in block in the way described above. However, the related art approach was difficult in achievement of such completely black-colored display in the image non-display sections. As a result, a decrease in quality has taken place.
As another method for displaying an image represented by a television signal on a liquid crystal display device that accommodates the XGA standard, a method is known which is for inputting the television signal to the driver circuit of the liquid crystal display device after acquiring or xe2x80x9cdownloadingxe2x80x9d to an associative personal computer and then converting and processing to a specific signal that corresponds in format to the XGA standard. In this case a separate device or circuit should additionally be required for conversion and processing of the television signal. Further, signal attenuation or degradation can occur due to the fact that the television signal must pass through such extra device or circuit, which would result in a decrease in image quality.
In accordance with one preferred practicing form of the present invention, a display device is provided which at least includes a plurality of TFTs, a signal generation means for generating a signal for use in determining the operation timing of said plurality of TFTs, a write control means for controlling outputting of said signal for determination of the operation timing, a means for outputting an externally supplied image signal to said TFTs on the basis of said signal for determination of the operation timing, and a display means for displaying an image based on said image signal, wherein said image signal is such that one is selected from among a plurality of image standards, wherein said display means has an image display section and an image non-display section for execution of displaying operations in a plurality of image standards, and wherein said write control means is operable to control the ratio of said image display section to said image non-display section of said display means. This may attain the foregoing objective.
Said image non-display section may be designed to display the color black.
It may also be arranged in a way such that said signal generation means is a shift register circuit while the operation of said shift register circuit is kept unchanged even when said image standard is changed.
Said image standard may be one selected from the group consisting of a television signal and a data signal from a computer.
In accordance with another practicing form of the present invention a display device is provided which at least comprises: an active matrix substrate which at least has a source line side driver circuit at least including a shift register circuit and a source line side write control circuit plus a switching circuit, a gate line side driver circuit at least including a shift register circuit and gate line side write control circuit, at least one TFT as disposed at a location in close proximity to an intersection between said source line and said gate line; an opposite substrate that oppose said active matrix substrate; and a display medium which is held between said active matrix substrate and said opposite substrate having its optical response as controlled by a voltage applied thereto, wherein said switching circuit is controlled by a signal from said source line side write control circuit while allowing an image signal as selected from among a plurality of image standards to be output to said source line and also causing a signal from said gate side write control circuit to be output onto a gate line. This may also attain the objective stated supra.
In the display device said display section for displaying said image signal may include an image display section and an image non-display section.
Said image non-display section may be designed to display the color black.
Said image standard may be either one of a television signal and a data signal from a computer.
Said display medium with its optical response as controllable by said voltage application may be either one of a liquid crystal device and an electro-luminescence device.